Method and structure for contacting an overlying electrode for a magnetoelectronics element

ABSTRACT

A method for contacting an electrically conductive electrode overlying a first dielectric material of a structure is provided. The method includes forming a mask layer overlying the electrically conductive electrode and patterning the mask layer to form an exposed electrically conductive electrode material. At least a portion of the exposed electrically conductive electrode material is removed while an electrically conductive veil is formed adjacent the mask layer. A metal contact layer is formed such that said metal contact layer contacts the electrically conductive veil.

FIELD OF THE INVENTION

The present invention relates generally to magnetoelectronics devices,and more particularly to a method and structure for contacting anoverlying electrode for a magnetoelectronics element.

BACKGROUND OF THE INVENTION

Magnetoelectronics devices, spin electronics devices and spintronicsdevices are synonymous terms for devices that use effects predominantlycaused by electron spin. Magnetoelectronics effects are used in numerousinformation devices, and provide non-volatile, reliable, radiationresistant, and high-density data storage and retrieval. The numerousmagnetoelectronics information devices include, but are not limited to,magnetic random access memory (MRAM), magnetic sensors and read/writeheads for disk drives.

Generally, a magnetoelectronics information device is constructed withan array of magnetoelectronics elements (e.g., giant magneto resistance(GMR) elements or magnetic tunnel junction (MTJ) elements) that areseparated by dielectric or other insulative material. Typically,electrical connection to a magnetoelectronics element is made viaelectrodes that overlie and underlie the element. However, inherentstress in the structure of the electrodes, particularly the overlyingelectrode, can adversely affect the magnetic properties of themagnetoelectronics element. Accordingly, it is preferable to make atleast the overlying contact electrode as thin as possible. However, asthe thickness of the overlying contact electrode decreases, thedifficulty in making subsequent electrical contact to the overlyingcontact electrode increases. Planarization to the overlying contactelectrode often results in over-planarization past the overlying contactelectrode. Further, the creation of vias to the overlying electrode isdifficult with present-day increases in aspect ratios and requiresadditional masking steps, resulting in decreased throughput andincreased production costs.

Accordingly, it is desirable to provide an efficient and cost-effectivemethod for contacting an overlying electrode for a magnetoelectronicselement. It is also desirable to extend use of this method to otherstructures in which contact to an electrode is required. Other desirablefeatures and characteristics of the present invention will becomeapparent from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments andtherefore do not limit the scope of the invention, but are presented toassist in providing a proper understanding. The drawings are not toscale and are intended for use in conjunction with the explanations inthe following detailed description. The present invention willhereinafter be described in conjunction with the appended drawings,wherein like reference numerals denote like elements, and:

FIGS. 1-7 illustrate schematically, in cross section, a method forcontacting an overlying electrode for a magnetoelectronics element inaccordance with an exemplary embodiment of the invention;

FIG. 8 illustrates schematically, in cross section, a structure inaccordance with an exemplary embodiment of the invention; and

FIG. 9 illustrates an enlarged perspective view of a portion of a randomaccess memory device in accordance with an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following detailed description is of exemplary embodiments only andis not intended to limit the invention or the application and uses ofthe invention. Rather, the following description provides a convenientillustration for implementing exemplary embodiments of the invention.Various changes to the described embodiments may be made in the functionand arrangement of the elements described without departing from thescope of the invention as set forth in the appended claims. Furthermore,there is no intention to be bound by any theory presented in thepreceding background or any exemplary embodiments of the invention.

FIGS. 1-7 illustrate a method for contacting an overlying (first)electrode 18 for a magnetoelectronics element 10, which may be a giantmagneto resistance (GMR) element or a magnetic tunnel junction (MTJ)element, in accordance with one embodiment of the invention. Asillustrated in FIG. 1, magnetoelectronics element 10 is preferably a MTJelement having a first magnetic layer 12, a tunnel barrier layer 14overlying first magnetic layer 12, and a second magnetic layer 16overlying tunnel barrier layer 14. Preferably, first magnetic layer 12is configured as a fixed magnetic layer and second magnetic layer 16 isconfigured as a free magnetic layer. First magnetic layer 12 overlies asecond electrode 20 and first electrode 18 overlies second magneticlayer 16. While second electrode 20 is illustrated in FIGS. 1-7, it willbe appreciated that second electrode 20 may not be necessary to theoperation of magnetoelectronics element 10 illustrated in the figuresand need not necessarily be present. The structure illustrated in FIG. 1may be formed in any conventional manner.

First and second magnetic layers (12, 16), and any additional magneticlayers, can be formed of any number of magnetic materials, such asnickel (Ni), iron (Fe), cobalt (Co) or alloys thereof. Alternatively,first and second magnetic layers (12, 16), and any additional magneticlayers, can be a composite magnetic material, such as nickel-iron(NiFe), nickel-iron-cobalt (NiFeCo) and cobalt-iron (CoFe) or alloysthereof, for example. Tunnel barrier layer 14, and any additional tunnelbarrier layers, is preferably aluminum oxide (Al₂O₃), but any number ofinsulators or semiconductors, such as aluminum nitride or oxides ofnickel, iron, cobalt or alloys thereof, can be used in accordance withthe present invention.

First and second electrodes (18, 20) can be formed of any suitableelectrically conductive materials. Preferably, first and secondelectrodes are formed of tantalum (Ta), aluminum (Al), tantalum nitride(TaN) or alloys thereof. More preferably, first and second electrodesare formed of tantalum.

Turning now to FIG. 2, a mask layer 22 may be formed overlying firstelectrode 18 using standard techniques known in the semiconductorindustry. Preferably, mask layer 22 is formed of a hardmask such as thatcomprising silicon dioxide, silicon nitride or any other suitabledielectric material. A photoresist layer 24 may be formed and developedoverlying mask layer 22 using standard photolithography techniques andmask layer 22 then may be etched to expose portions 26 of firstelectrode 18. The etch may be a wet etch, such as an etch inhydrofluoric acid or other similar fluid, a dry etch such as in aplasma, or any other etch known in the semiconductor industry suitablefor etching mask layer 22. In an alternative embodiment of theinvention, mask layer 22 and photoresist layer 24 may comprise onecontiguous masking layer formed of photoresist, which is patterned usingstandard photolithography techniques to expose portions 26 of firstelectrode 18.

Referring to FIG. 3, exposed portions 26 of first electrode 18 are thenremoved preferably by plasma sputtering using standard reactive ionetching (RIE) processing using mask layer 22 as a sputter etch mask.During the sputtering process, a portion of the electrically conductivemolecules released from exposed portions 26 of first electrode 18deposits on the sidewalls of mask layer 22, thus forming an electricallyconductive veil 28 in electrical contact with the remaining portion offirst electrode 18. Veil 28 may also form along the sidewalls ofphotoresist layer 24. It will be appreciated that the amount of materialcomprising veil 28 can be increased or decreased by changing thereactive components of the etching process, such as for example,temperature, bias of the process, the amount of reactive gas etchant,etc., such that more or less material from first electrode 18 isreleased from exposed portions 26 and deposited as veil 28. It also willbe appreciated that, while plasma sputtering is the preferred processfor removing exposed portions 26 of first electrode 18, any suitablemethod for removing exposed portions 26 of first electrode 18 while alsoforming veil 28 along the sidewalls of mask layer 22 may also be used.Such methods may include, for example, ion milling and inert gas sputteretching.

Removal of exposed portions 26 of first electrode 18 exposes portions 30of second magnetic layer 16. As illustrated in FIG. 4, in accordancewith one embodiment of the invention, exposed portions 30 of secondmagnetic layer 16 may be removed by any suitable method, such as, forexample, ion milling or chemical or non-reactive RIE processing, usingpatterned first electrode 18 and veil 28 as a sputter etch mask. Duringthe sputtering process, a portion of the electrically conductivemolecules from exposed portions 30 of second magnetic layer 16 arereleased and may further deposit on existing veil 28 and on thesidewalls of mask layer 22, thus further growing veil 28. It isbelieved, however, that it may not be necessary to the principles of theinvention for molecules from magnetic layer 16 to be included in veil28, and thus veil 28 may be composed of materials different from secondmaterial layer 16.

Photoresist layer 24 then may be removed by any standard photoresistremoval technique known in the semiconductor industry, as illustrated inFIG. 4. If mask layer 22 and photoresist layer 24 are both formed ofphotoresist, as in one continuous layer of photoresist, upon removal ofthe photoresist, veil 28 will, in effect, from a hollow “well” withfirst electrode 18 as its base.

It will be appreciated that, in a preferred embodiment of the invention,exposed portions 30 of second magnetic layer 16 are completely removed,as illustrated in FIG. 4. In an alternative embodiment of the invention,the sputter etch process may be terminated before etching through theentire thickness of second magnetic layer 16 so that a residual amountof exposed portions 30 of second magnetic layer 16 remains. In thisembodiment, the residual amount of exposed portions 30 of secondmagnetic layer 16 may be oxidized using any suitable method known in thesemiconductor industry. During the oxidation of second magnetic layer16, photoresist layer 24 also is removed by the oxidation.

Referring to FIG. 5, a dielectric material layer 32 may then be formedoverlying veil 28, any exposed mask layer 22, and remaining exposedportions 34 of magnetoelectronics element 10. It will be appreciatedthat if mask layer 22 was formed of photoresist and had been earlierremoved such that veil 28 formed a hollow “well,” dielectric materiallayer 32 would now fill the well. Dielectric material layer 32 may beformed of any suitable dielectric material such as, for example,plasma-enhanced oxide, nitride and the like. Preferably, dielectricmaterial layer 32 is formed by plasma-enhanced chemical vapor deposition(PECVD), although dielectric material layer 32 may be formed by anyother suitable process such as physical vapor deposition (PVD), chemicalsolution deposition (CSD), pulsed laser deposition (PLD), and the like.

As illustrated in FIG. 6, a portion of the dielectric material layer 32is then removed to expose an area 36 of veil 28. A sufficient area 36 ofelectrically conductive veil 28 should be exposed so that a subsequentlyformed metal contact, discussed in more detail below, can makeelectrical contact with first electrode 18 via veil 28, as veil 28extends along the sidewalls of mask 22 (or “well” of dielectric, as thecase may be) to first electrode 18. Dielectric material layer 32 may beremoved by chemical mechanical planarization (CMP), etching, sputteringor any other suitable method. Preferably, a substantial first thicknessof dielectric material layer 32 is removed by CMP and then a secondthickness of dielectric material layer 32 is removed by sputtering usingstandard techniques known in the semiconductor industry to achieve adesired residual thickness of the layer.

Turning now to FIG. 7, electrical contact to overlying first electrode18 is completed, in accordance with one embodiment of the invention, bydepositing a metal contact layer 38 overlying dielectric material layer32 and contacting exposed areas 36 of electrically conductive veil 28.Metal contact layer 38 can be suitably patterned in any known manner toform the desired electrode pattern. Metal contact layer 38 may be formedof any suitable conductive metal such as copper (Cu), aluminum (Al) andthe like. As described above, metal contact layer 38 is electricallycoupled to first electrode 18 via electrically conductive veil 28, whichextends between metal contact layer 38 and first electrode 18.

It will be appreciated that the principles of the present invention arenot limited to magnetoelectronics structures but may also be used forcontacting a first electrically conductive electrode of any structurehaving a first electrically conductive electrode overlying a dielectricmaterial. In accordance with another exemplary embodiment of the presentinvention, FIG. 8 illustrates an electronic structure 40 formed usingthe various embodiments of the method described above. Structure 40includes an electrically conductive electrode 42 overlying a firstdielectric material layer 44. Electrically conductive electrode 42 canbe formed of any material suitable for a particular application.Electrical contact to electrode 42 is achieved by a metal contact layer48, which is electrically coupled to electrically conductive electrode42 by an electrically conductive veil 46. Veil 46 is formed by removingexposed portions of electrode 42 using a mask layer 52 as a sputter etchmask. Metal contact layer 48 may be formed of any of the materialscomprising metal contact layer 38 as described with reference to FIG. 7.Metal contact layer 48 contacts veil 46 at exposed areas 50, which areof sufficient areas so that electrical contact with electrode 42 isachievable. A second dielectric material layer 54 may overlie firstdielectric material layer 44 and insulate veil 46.

FIG. 9 illustrates an enlarged perspective view of a portion of a randomaccess memory device 70 in accordance with another exemplary embodimentof the present invention. Elements of FIG. 9 that have the samereference numbers as FIG. 7 are the same as the corresponding FIG. 7elements. Random access memory device 70 includes a plurality ofmagnetic memory units 72 that are each electrically coupled to a metalcontact layer 38. The magnetic memory units 72 may be formed on anysuitable substrate 74, which may include any suitable semiconductordevices (not shown) such as, for example, switching transistors, bitand/or data lines, input/output circuits, data/address decoders, and thelike.

Each magnetic memory unit 72 includes a first electrode 18, amagnetoelectronic element 10 underlying first electrode 18, a secondelectrode 20 underlying magnetoelectronic element 10, and anelectrically conductive veil 28. Electrically conductive veil 28electrically couples first electrode 18 to metal contact layer 38. Adielectric material layer 32 is formed to cover the exposed portions ofsubstrate 74, the exposed portions of magnetoelectronic element 10 andelectrically conductive veil 28. Accordingly, when an electric currentis applied to metal contact layer 38, it may flow from metal contactlayer 38 to first electrode 18, then through magnetoelectronics element10 to second electrode 20 and on to any other electrical path asprovided for in substrate 74.

From the foregoing description, it should be appreciated that a methodfor contacting an overlying electrode for a magnetoelectronics elementis provided that presents benefits that have been presented in theforegoing background and description and also presents benefits thatwould be apparent to one skilled in the art. Furthermore, while apreferred exemplary embodiment has been presented in the foregoingdescription, it should be appreciated that a vast number of variationsin the embodiments exist. Lastly, it should be appreciated that theseembodiments are preferred exemplary embodiments only, and are notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the foregoing detailed descriptionprovides those skilled in the art with a convenient road map forimplementing a preferred exemplary embodiment of the invention. It beingunderstood that various changes may be made in the function andarrangement of elements described in the exemplary preferred embodimentwithout departing from the spirit and scope of the invention as setforth in the appended claims.

1-16. (canceled)
 17. A random access memory device having a metalcontact layer and a plurality of magnetic memory units electricallycoupled to the metal contact layer, each magnetic memory unitcomprising: a magnetoelectronics element; an electrode overlying saidmagnetoelectronics elements; and an electrically conductive veil,wherein said electrically conductive veil electrically couples saidelectrode and said metal contact layer.
 18. The random access memorydevice of claim 17, said electrically conductive veil comprised of amaterial of which said electrode is comprised.
 19. The random accessmemory device of claim 17, said magnetoelectronics element having amagnetic layer, wherein said electrically conductive veil is comprisedof materials that comprise said electrode and said magnetic layer. 20.The random access memory device of claim 17, said magnetoelectronicselement comprising one of a magnetic tunnel junction element and a giantmagneto resistance element.
 21. The random access memory device of claim17, wherein at least one insulating layer is disposed between saidelectrode and said metal contact layer.
 22. The random access memorydevice of claim 21, said at least one insulating layer comprising a masklayer.
 23. A semiconductor structure for making contact to an electrode,the semiconductor structure comprising: an electrode; an electricallyconductive contact layer; at least one insulating layer disposed betweensaid electrode and said electrically conductive contact layer; and oneof a sputter by-product of said electrode and an etch by-product of saidelectrode that electrically couples said electrode and said electricallyconductive contact layer.
 24. The semiconductor structure for makingcontact to an electrode of claim 23, wherein one of a sputter by-productof said electrode and an etch by-product of said electrode extends fromsaid electrode to said electrically conductive contact layer.
 25. Thesemiconductor structure for making contact to an electrode of claim 23,said at least one insulating layer comprising a mask layer.
 26. Thesemiconductor structure for making contact to an electrode of claim 23,said one of a sputter by-product of said electrode and an etchby-product of said electrode comprising a sputter by-product of saidelectrode produced by reactive ion sputtering.
 27. The semiconductorstructure for making contact to an electrode of claim 23, wherein saidelectrode is electrically coupled to a magnetoelectronics element.
 28. Asemiconductor structure for making electrical contact to amagnetoelectronics element, the semiconductor structure comprising: anelectrode overlying the magnetoelectronics element; an electricallyconductive contact layer overlying said electrode; at least oneinsulating layer disposed between said electrode and said electricallyconductive contact layer; and an electrically conductive veil thatextends from said electrode to said electrically conductive contactlayer.
 29. The semiconductor structure for making electrical contact toa magnetoelectronics element of claim 28, said electrode comprising atleast one material selected from the group consisting of tantalum,aluminum, tantalum nitride, and combinations thereof.
 30. Thesemiconductor structure for making electrical contact to amagnetoelectronics element of claim 28, said at least one insulatinglayer comprising a mask layer.
 31. The semiconductor structure formaking electrical contact to a magnetoelectronics element of claim 28,said electrically conductive veil formed by one of sputtering saidelectrode and etching said electrode.
 32. The semiconductor structurefor making electrical contact to a magnetoelectronics element of claim28, said magnetoelectronics element having a magnetic layer, whereinsaid electrically conductive veil is comprised of materials thatcomprise said electrode and said magnetic layer.
 33. The semiconductorstructure for making electrical contact to a magnetoelectronics elementof claim 28, said magnetoelectronics element comprising one of amagnetic tunnel junction element and a giant magneto resistance element.